Sun 's collision

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alendar_zhana

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Hello
I DO NOT STUDY ASTRONOMY OF PHYSICS AND I HAVE A QUESTION:
When the Sun expands before it's collidion, on the graphic it seems that the planets around it are just staying at the same position and distance they used to before the Sun started collinding and orbiting the same way? Now, since the Sun is changing its form, core(running out of power) aren't the planets suppose to change at least the way they orbit around it, may be... the gravity of the sun will change or...the palnets will get pushed away as the Sun mass and "power" changes too???? If someone can answer that I would really appreciate it!
 
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dangineer

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I think you are refering to the expansion of the sun during the end of it's life. If that is what you are talking about, then you are correct. The planets' orbits will change for a couple of reasons:

As the sun expands, it's atmosphere will expand to envelope the planets closest to it. This will cause one of two things, either the planet will slow down and be drawn into the sun due to drag, or the increasing force of the solar wind will push the planet further out. Also, late in it's life, the sun will begin throwing off mass towards the outer solar system, thus the sun will be less massive and the planets' orbits will expand due to the decreased gravity.

Hope that helps and welcome to Space.com!
 
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MeteorWayne

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This thread would be better off in Ask the Astronomer, than here in Physics, so I will move it.

MW
 
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alendar_zhana

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MeteorWayne":1nr090l8 said:
This thread would be better off in Ask the Astronomer, than here in Physics, so I will move it.

MW
Thank you
 
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neilsox

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Small objects such as comets collide with the Sun each year. This typically adds mass to the sun, which causes the planets to move closer, perhaps as much as a millimeter. Other mechanisms are causing the planets to increase the length of their orbits, such as the sun converting mass to energy = fusion. The net change is too small to measure.
A very fast, very high density object with a mass several times that of the Sun, such as a black hole, could not only collide, but could pass through the Sun and keep going in about the same direction. Several percent to more than half of the mass of the sun might follow the intruder out of the exit hole. The reduced mass of the sun could double the orbital radius of all the planets. Except even the brief presence of the intruders strong gravity would perturb the orbits of the planets at least slightly, perhaps cancelling part of the orbital radius increase. It may be billions or even trillions of years before a massive object collides with our Sun, so not to worry. Neil
 
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